Field of Invention
The present invention relates to a preparation method of a compound, and more particular to a preparation method for ferrate.
Description of Related Arts
Ferrate has a strong oxidizing function under a relatively wide pH range and is capable of oxidizing many organic or inorganic substances. For examples, inorganic compounds such as NH2+, S2O32−, SCN−, H2; heavy metals such as Arsenic and chromium; radioactive substances such as uranium; and organic compounds such as alcohols, acids, amines, hydroxyl-ketones, hydroquinones and phenols. Ferrate is an ideal, highly effective and highly selective oxidant which will not cause any damaging effect to humans and other living organisms or to the environment. Also, ferrate ions in aqueous solution can kill E. coli and general bacteria, and remove the hazardous organic substances, —NO2−, poisonous Cn− and etc. in wastewater. In addition, the Fe(OH)3 produced by decomposition of ferrate ions can be used as an adsorption agent to adsorb different kinds of cations and anions and thus a very good water purification function is provided. Accordingly, ferrate is also an ideal water treatment agent for industrial wastewater and drinking water. However, since the preparation process of ferrate is complicated and the investment cost is high, large scale application of ferrate salts is restricted.
At present, a more common approach is to utilize the wet oxidation method to prepare ferrate salts. For the applications of wet oxidation to prepare ferrate salts, a lot of researches have been done by many domestic and foreign scholars. U.S. Pat. No. 6,331,949 disclosed a preparation method which uses potassium hydroxide, chlorine, ferric chloride, silicate and iodate to produce ferrate. The Japan patent Kokai 80/75926, which was published in T. Morishita on Jun. 7, 1980, disclosed a preparation method which uses the molten iron or iron oxide with potassium nitrate and potassium hydroxide to produce ferrate. The patent number EP19820305914 disclosed a preparation method which uses potassium hypochlorite and ferric salts with adding strongly alkaline reagent to produce ferrate. However, since the ferrate solution is very unstable, dimethylsulfoxide, dimethyl sulfone and methanol are used in the ferrate purification process. U.S. Pat. No. 5,217,584 disclosed that beta-ferric oxide is used as the iron source, iodine-containing or tellurium-containing salt of sodium potassium are used as the stabilizing compounds, and hypochlorous acid is utilized to produce ferrate, where the reaction temperature is 18˜25° C. and the reaction time is 1˜6 hours. In the patent number CN101497461A, a rapid preparation process for ferrate solution which uses Iron (II, III) oxide as the iron source for reaction under microwave irradiation condition is disclosed.
The above papers do not teach or suggest any ferrate preparation method which utilizes iron in nascent state as the iron source, wherein the papers regarding chemical wet method mostly utilizes iron salts such as ferric chloride, ferric sulfate or ferric nitrate as the iron source.